1. Field of the Invention
This invention relates to doorsill assemblies and, in particular, to adjustable thresholds for use in such doorsill assemblies.
2. Description of the Related Art
Over the years, a wide variety of doorsill assemblies have been made with adjustable thresholds. Door sill assemblies were initially designed to fit immediately below an entryway door but are now often extended to adjacent side lights to provide a continuous sill having a uniform, aesthetic appearance while forming a water tight juncture between the sill and the adjoining building floor surface. Such doorsill assemblies also prevent the door from swinging too far forward in the frame so that the hinges are not damaged.
Adjustable sills were developed to provide a threshold which an installer can adjust to fit a specific door. By maintaining a predetermined clearance between the threshold and the door, a door seal can effectively keep out wind and water. Being closest to the ground, the threshold and its juncture with the door is the first line of contact between outside water and cold air and the environment inside the door.
It is desirable that adjustable thresholds be easy to install and adjust, structurally sound, relatively inexpensive and aesthetically pleasing. Another important feature in cold climates is that the threshold should provide a good thermal barrier in order to prevent condensation and icing on the portion of the threshold within the building interior.
With the advent of adjustable sills, it was no longer as necessary to ensure that the measurements of the door, its fit in the frame, or otherwise were exact as the adjustable threshold could be used to provide the seal between the threshold and the door. As a result, construction could be faster, quicker, and even better as the threshold could be adjusted for the best position after the door and threshold had been installed.